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    <meta charset="UTF-8">
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    <title>使用const命令声明常量</title>
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<body>
    <script>
        const PI = 3.14159;
        console.log(PI); //3.14159
        PI = 3;
        console.log(PI);

        
        //TypeError:Assigment to constant variable.
    </script>
</body>
</html>